Incidence of malignant melanoma of the skin in Norway, 1955–1970.Variations in time and space and solar radiation

Time trends and geographical variations in incidence were analyzed for malignant melanoma of the skin in Norway, 1955–1970. A total of 2541 new cases were registered. During the 15 year period the age-adjusted incidence rate was more than doubled for both sexes. A marked north-south gradient was observed, the incidence in Southern Norway being, almost 3 times larger than that in the Northern part of the country. Variations in time and space were most pronounced for malignant melanoma of the male neck-trunk and the female lower limb, and large cohort variations between those born around the century up to those born around 1935 were observed. It is concluded that the increase in incidence in the main must be real. The epidemiologic contrasts indicate that exposure to sunlight is an important factor in the etiology of malignant melanoma of the skin. The effect of exposure seems to be local. No support is given to the hypothesis of a systemic effect.